This study will provide information regarding the extent to which the glycerol-induced hyperhydration (GIH) will reduce the orthostatic intolerance resulting from bedrest, a 1 g model of microgravity. Eight subjects will be confined to bedrest (6 degree head down) for 7 days. Presyncope Lower Body Negative Pressure (PLBNP) will be conducted prior to the bedrest and the Standard LBNP tests will be conducted prior to the bedrest and the Standard LBNP will be repeated on days 4 and 7.